Garden Myths Busted: Willow Water, Garlic and Peroxide

Two horticultural professionals took some of the most popular garden myths into the university laboratory to prove or disprove the accuracy of these myths. Dr. Linda Chalker-Scott from Washington State University and Dr. Jeff Gilliam from the University of Minnesota tested these myths under controlled conditions to determine if they really work.

The Myth: Soaking plant cuttings in a tea made from willow stems will benefit and speed up the root production.

The Facts: There are many commercial rooting hormones available to promote and speed up root development on cuttings. These growth hormones are called auxins. In the 1950s horticulturalist C.E. Hess discovered that willow diffusate or willow water greatly improved rooting success. Willow water is actually a tea or slurry made by placing 50 to 100, 6-inch-long willow twigs into a gallon of water. The mixture is left to brew for 4-6 weeks. The mixture is strained and the remaining liquid is used to root cuttings.

The theory is that if a certain plant is proflic and easy to root it must contain some substance that promotes root development. We all know how quickly willow trees grow and spread their roots. Willow contains salicylic acid better known as aspirin. Aspirin is an ethylene inhibitor. Ethylene negatively affects root development. So by decreasing the effectiveness of ethylene it could have a positive effect on root development.

Most of the research done on willow water was conducted using young plants. Commercial rooting hormones containing indole-3-butyric acid or naphthalene-3-acetic acid provided much better results on harder-to-root cuttings. The verdict? You can be your own judge. You may want to use willow water on easily rooted cuttings but use a commercial product on the harder to root cuttings.

The Myth: Garlic will repel insects.

The FactsWe all know how repulsive it is to get close to someone who has eaten too much garlic; insects also find the odor of garlic iepulsive. There are many forms of commercial garlic products available extracts, oils, sprays and the familiar bulbs of fresh garlic. Very little research was done to determine if garlic was an effective repellent until the 1970s, although some research in the 1950s that determined garlic did indeed repel ticks. In the 1990s a group of researches put together a connotation that was effective in repelling insects.

The Recipe

5 ounces garlic extractSeveral drops of liquid dish soap1 quart water

Blend this mixture wellStrain through two layers of cheese clothDilute this mixture to 10% of the original concentrationSpray onto affected pants.

This mixture does not kill insects only repels them. If parts of the plant are not sprayed the insects will move to that area of the plant. This spray has shown to be especially effective on whiteflies, aphids and most beetles. The downside is that your plants will smell like garlic for up to two weeks. However, if you're absolutely against commercial insecticides this might be just the solution for you insect problems.

The Myth: Hydrogen peroxide is an effective fungicide and spraying the leaves of your plants will prevent fungal diseases.

The FactsA 3 percent peroxide solution was applied once a week to rose bushes. The application did nothing to deter either blackspot or powdery mildew. Hydrogen Peroxide is a very unstable chemical. It is very similar to plain water and breaks down very quickly. It is very helpful if you want to sterilize something but doesn't last long enough to be effective on controlling disease in an outdoor environment.

The Myth: A plant under stress should be fertilized

The FactsFertilizing a plant that is not lacking nutrients can actually add to the stress that the plant is experiencing. Usually when a plant is stressed it is not from a lack of food. Compacted soil, poor planting practices, heat, over-watering or under-watering, are the most common causes of stress. Ensuring that the plant is well hydrated but not overwatered is the first step in taking a plant out of stress.

The Myth: Organic pesticides are less toxic than synthetic ones.

The TruthMisuse of pesticides whether they are organic or synthetic can be harmful. Pyrethrum is made from chrysanthemums but is still toxic to humans and pets if handled improperly. When addressing a problem with plants whether it be insect or disease its best to select the least toxic control option. Read and follow all label instructions whether it is organic or synthetic.

In closing, I expect some of you might disagree with some of these findings. However remember that this research was done in reputable university labs under controlled conditions. Each of us will draw our own conclusions.

About Paul Rodman

Paul Rodman has been gardening for over 45 years. He is an Advanced Master Gardener, and American Rose Society Consulting Rosarian. He is President Emertius of the Western Wayne County Master Gardener Association in Wayne County, Michigan. He currently serves as the greenhouse chairman of this group. Rodman has amassed over 5500 volunteer hours in the Master Gardener program.
Rodman is the garden columnist for The News Herald newspaper, in Southgate, Michigan. He has also written for the Organic Gardening.com web site.
He is a certified Master Canner and has taught classes on Home Food Preserving for 7 years.
He has lectured on various gardening topics throughout southeastern Michigan.
His favorite pastime is teaching children about gardening. For the past several years he has conducted classes for second grade students teaching them about subjects ranging from vermi-composting to propagation.